For what it's worth, when I first read this description, my initial thought was that the Alber would swing back almost into Tail.
From there, the sword can be launched out with the step in a sidearm throwing motion like one would imagine a sling being used.
However, according to
www.slinging.org, a classic sling can be used overhand, sidearm, or underhand. This makes me wonder if the strike becomes a one handed scheitelhau from Tail.
Another question is if the extension of range is done through das gayzlen type of holding only at the pommel with the bottom hand (which seems implausible) or possibly letting the pommel slide up to the top hand (ending in an awkward reaching position).
Either way, if my novice interpretation is correct, it seems to be a wild strike in a large arc that would be easily avoided, parried, or countered by someone with more experience than me. And even if I'm way off, I offer this post in an academic effort to explore all possibilities.
FYI
"Slinging
Miscellaneous Handwork: A flinging cut delivered from a distance.
schlaudern: Egenolph 6r; Meyer 19r, 60r, 60v [MnG schleudern]"
http://www.higginssword.org/guild/study/glossary/#slinging "Schlaudern
'Slinging' An overhand slinging blow akin to Das Gayszlen".
http://www.thearma.org/terms2.htm